Catheter with composite stiffener

ABSTRACT

A catheter comprising an elongate tubular member having a proximal end, a distal end, and a passageway defining a lumen extending between the proximal and distal ends. The elongate tubular member comprises a relatively stiff proximal section and a relatively flexible distal section. The proximal section includes an inner tubular liner, a first stiffener comprising a metal alloy, and a second stiffener comprising a non-metal alloy. The first and second stiffeners are coaxially wound exterior to the proximal inner liner. The distal section includes a distal inner tubular liner and the second stiffener coaxially wound exterior to the distal inner liner. The first stiffener terminates before reaching the distal section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/045,102, filed Mar. 10, 2011, now U.S. Pat. No. 8,317,772; which is acontinuation of U.S. application Ser. No. 11/516,061, filed Sep. 6,2006, now U.S. Pat. No. 7,909,812; which is a continuation of U.S.application Ser. No. 10/079,103, filed Feb. 19, 2002, now U.S. Pat. No.7,104,979; which is a continuation of U.S. application Ser. No.09/096,267, filed Jun. 11, 1998, now U.S. Pat. No. 6,368,316; the entiredisclosures of which are all incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to catheters, and more particularly, toa catheter with a composite stiffener.

BACKGROUND OF THE INVENTION

Catheters are increasingly used to access remote regions of the humanbody and, in doing so, delivering diagnostic or therapeutic agents tothose sites. In particular, catheters which use the circulatory systemas the pathway to these treatment sites are especially practical.Catheters are also used to access other regions of the body, e.g.,genito-urinary regions, for a variety of therapeutic and diagnosticreasons. One such treatment of diseases of the circulatory system is viaangioplasty (PTA). Such a procedure uses catheters having balloons ontheir distal tips. It is similarly common that those catheters are usedto deliver a radiopaque agent to the site in question prior to the PTAprocedure to view the problem prior to treatment.

Often the target which one desires to access by catheter is within asoft tissue such as the liver or the brain. These are difficult sites toreach. The catheter must be introduced through a large artery such asthose found in the groin or in the neck and then be passed throughever-narrower regions of the vascular system until the catheter reachesthe selected site. Often such pathways will wind back upon themselves ina multi-looped path. These catheters are difficult to design and toutilize in that they must be fairly stiff at their proximal end so toallow the pushing and manipulation of the catheter as it progressesthrough the body, and yet must be sufficiently flexible at the distalend to allow passage of the catheter tip through the loops andincreasingly smaller blood vessels mentioned above and yet at the sametime not cause significant trauma to the blood vessel or to thesurrounding tissue. Further details on the problems and an early, butyet effective, way of designing a catheter for such a traversal may befound in U.S. Pat. No. 4,739,768 to Engelson. These catheters aredesigned to be used with a guidewire. A guidewire is simply a wire,typically of very sophisticated design, which is the “scout” for thecatheter. The catheter fits over and slides along the guidewire as itpasses through the vasculature. Said another way, the guidewire is usedto select the proper path through the vasculature with the urging of theattending physician and the catheter slides along behind once the properpath is established.

There are other ways of causing a catheter to proceed through the humanvasculature to a selected site, but a guidewire-aided catheter isconsidered to be both quite quick and somewhat more accurate than theother procedures. One such alternative procedure is the use of aflow-directed catheter.

This invention is an adaptable one and may be used in a variety ofcatheter formats. The construction technique has the benefit ofproducing catheter sections having small overall diameters but withexceptional strength, resistance to kinking, and recovery from kinking(even in vivo) should such kinking occur. The catheter may be used inconjunction with a guidewire, but the catheter may also be used as aflow-directed catheter with the attachment of a balloon or incombination with a specifically flexible tip.

The use of a braid or coil in a catheter body is not a novel concept.Typical background patents are discussed below. However, none of thesedocuments have used the concept of this invention to produce a catheterhaving the structure and physical capabilities of the catheter of thisinvention.

U.S. Pat. No. 5,454,795 discloses a kink-free spiral wound catheter. Thecatheter includes a stiffener ribbon, typically metallic, spirally woundwithin the catheter body to create a catheter having controllablestiffness. The stiffener is included in a distal section of thecatheter.

U.S. Pat. No. 5,702,373 shows a catheter having a reinforced braidtypically of superelastic alloy ribbon located in a distal section ofthe catheter. The superelastic alloy ribbon provides high resistance tokinking.

SUMMARY OF THE INVENTION

This invention is a catheter having a) a more proximal sectionpreferably made up of an inner tubular liner, a first stiffenercomprising a metal alloy, and a second stiffener comprising a non-metalalloy, the first and second stiffeners being coaxially wound exterior tothe proximal inner liner; and b) a more distal section comprising adistal inner tubular liner, and the second stiffener coaxially woundexterior to the distal inner liner. The first stiffener desirablyterminates before reaching the distal section to provide a more flexibledistal section. Other sections of these or other designs may be placedvariously between the noted sections or distal of the distal sectiondescribed above.

The stiffeners may be wound in a number of different ways. For example,the stiffener may comprise a single strand of ribbon wound in a singledirection or multiple strands interwoven in a braid. The first andsecond stiffeners may be independently wound as a coil or braid or maybe interwoven to form a single braid. The first stiffener may includeribbons formed of a superelastic alloy such as nitinol, for example. Themetal stiffener provides kink resistance to the proximal section of thecatheter. The second stiffener may include a polymer such as liquidcrystal polymer, polyurethane, polyimide, polyethylene, polyethyleneterephthalate, or Nylon, for example. The second stiffener is desirablymade from a material which is capable of being permanently deformed whenexposed to steam so that the catheter may be shaped to have variousbends for a specific surgical procedure.

The catheter may also have an outer cover exterior to the stiffener. Theinner tubular liner and outer cover may be of a polymeric composition. Alubricious coating may be applied to the outer surface of the outercover or the inner surface of the inner liner.

The catheter assembly may also have such ancillary components as aluer-lock and some manner of providing radiopacity.

The above is a brief description of some deficiencies in the prior artand advantages of the present invention. Other features, advantages, andembodiments of the invention will be apparent to those skilled in theart from the following description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a typical three section catheter made using theconcepts of this invention;

FIG. 2 is a schematic cross-sectional view of proximal and distalsections of a catheter;

FIG. 2A is a cross-sectional view of an alternate portion of a catheter;

FIG. 3 is a schematic cross-sectional view of alternate proximal anddistal sections of a catheter;

FIG. 4 is an enlarged side view of a section of a catheter having aribbon helically wound on an inner tubular liner;

FIG. 5 is an enlarged side view of the section of FIG. 4 with a secondribbon helically wound over the first ribbon;

FIG. 6 is an enlarged side view of a catheter section having two ribbonsinterwoven to form a braid between an inner liner and an outer cover,with parts being broken away to show detail;

FIG. 7 is a schematic cross-sectional view of alternate proximal anddistal sections of a catheter; and

FIG. 8 is a schematic cross-sectional view of proximal and distalsections of a catheter.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF THE INVENTION

This invention is a catheter assembly having a more distal sectionpreferably made up of an inner liner, an outer cover, and a stiffenercomprising a non-metal alloy, and a more proximal section comprising aninner liner, an outer cover, and a stiffener comprising a metal alloyand a non-metal alloy. The stiffeners are interposed between the innerliner and outer cover. Other sections of these or other designs may beplaced variously between the noted sections or distal of the distalsection noted above.

A typical multi-section catheter 100 which may incorporate the conceptsof this invention is shown in FIG. 1. Such a catheter is described inmore detail in U.S. Pat. No. 4,739,768 to Engelson, the entirety ofwhich is incorporated by reference and is particularly suitable forneurological and peripheral vascular applications. It is also suitablefor less demanding service such as might be encountered in access andtreatment of the heart. One difficulty which has arisen as higherdemands for length have been placed on these catheters is that thediameter of the distal section necessarily becomes smaller and smaller.This is so since the longer catheters must reach ever smaller vascularareas. This smaller diameter requires a concomitant thinning of the wallsection. The thinner section walls may kink or ripple when activelypushed along the guidewire or when vaso-occlusive devices are pushedthrough the catheter's lumen. The typical configuration shown in FIG. 1has a distal section 102 having significant flexibility, an intermediatesection 104 which is typically less flexible, and a long proximalsection 106 which in turn is least flexible. The distal section 102 isflexible and soft to allow deep penetration of the extraordinaryconvolutions of the neurological vasculature without trauma. Variousknown and often necessary accessories to the catheter assembly, e.g.,one or more radiopaque bands 108 at the distal region to allow viewingof the position of the distal region under fluoroscopy and a luerassembly 110 for guidewire 112 and fluids access, are also shown inFIG. 1. The typical dimensions of this catheter are:

-   -   Overall length: 60-200 cm    -   Proximal Section (106): 30-150 cm    -   Intermediate Section (104): 20-50 cm    -   Distal Section (102): 2.5-30 cm

Obviously, these dimensions are not particularly critical to thisinvention and are selected as a function of the malady treated and itssite within the body. Typical of the catheters made using this inventionare those in the 2 French to 5 French range (1 French=0.013 inch). Theinner diameter of such catheters is then 10 mils. to 42 mils. (1mil=0.001 inch).

Furthermore, a catheter made using this inventive concept need not be ofthree sections with increasing stiffness as is shown in FIG. 1. Thecatheter may be of two discrete sections or may be of four or morediscrete sections of differing flexibility. Through judicious choice ofphysical parameters for the catheter sections, the components may alsohave varying physical parameters (e.g., lubricity, flexibility, wallthickness, inner or outer layer member composition, etc.) within thesections. Typically, although not necessarily, when a three sectioncatheter is desired, the most proximal section 106 is the “moreproximal” or “stiff” section described herein. Again, although notnecessarily, when a three section catheter is desired, the most distalsection 102 is the “more distal” or “flexible” section. The distalsection 102 may be the distal end of the catheter.

FIGS. 2 and 3 illustrate two catheter portions, generally indicated at120 and 122, and having a proximal section 124, 126 and a distal section128, 130, respectively. The distal section 128, 130 may be at the distalend of the catheter, or there may be another section located distally ofthe distal section. The catheter portions are elongate tubular membershaving a proximal end, a distal end, and a passageway defining a lumenextending between the proximal and distal ends. Referring to FIG. 2, thecatheter portion 120 preferably includes an inner tubular liner 132, anouter cover 134, and a stiffener coaxially wound and interposed betweenthe inner liner and the outer cover. The stiffener is formed from afirst stiffener 140 comprising a metal alloy and a second stiffener 142comprising a non-metal alloy. The metal stiffener 140 terminates beforereaching the distal section 128 so that only the non-metal stiffener 142is located within the distal section. This allows the distal section 128to be heated by, for example, exposure to steam, and permanentlydeformed so that the distal section can be bent into a specificconfiguration corresponding to vasculature through which the catheter isto be inserted. For example, the distal section 128 of the catheter maybe exposed to steam (212° F.) and formed around a mandrel. This allowsthe shaping of the distal section 128 to be accomplished at the time ofsurgery while the vasculature is being viewed. The metal stiffenerswhich are typically present in conventional catheters prevent thereshaping of the distal section of the catheter since the metal itselfcan not be reshaped by steam heating.

The stiffener may be formed with one or more coils or braids. Forexample, a metal strand may be helically wound onto the inner liner 132,and a non-metal strand may be helically wound on top of the metalstrand. Alternatively, the stiffener may be formed from a metal strandinterwoven with a non-metal strand to form a braid. The first and secondstiffeners may also be individually formed as a separate braid from twoor more strands. It is to be understood that the shape of the strands,number of strands, and arrangement of the strands may be different thanshown in FIGS. 2 and 3 or described herein without departing from thescope of the invention. For example, the strand may be a wire having acircular or oval cross-sectional shape. Wire strands having a circularor oval cross-sectional shape are illustrated in FIG. 8 at 140 and 142.Typical coil and braid stiffeners which may be used in the proximal ordistal sections are shown in FIGS. 4-6.

FIG. 4 shows a magnified section of a catheter body which may be used asa distal section of a catheter. The catheter section includes the innertubular liner 132 and a stiffener which comprises a helically woundribbon 150. The ribbon 150 may be simply wound onto the inner liner 132or the ribbon may be applied with an adhesive. The number of turns orpitch of the ribbon 150 may vary along the length of the section orcatheter to control the overall stiffness of the section or catheter.

FIG. 5 shows the catheter section of FIG. 4 with the helically woundstiffener ribbon 150 wound in a first direction or “handedness” and asecond stiffener ribbon 152 wound in a second direction or “handedness”around both the first stiffener ribbon and the inner tubular liner 132.

A catheter section having a stiffener comprising a braid member 156interposed between the inner tubular liner 132 and the outer cover 134is shown in FIG. 6. The braid member 156 may be made up of a suitablenumber of ribbons, typically four or more. The ribbons are interwoven inan in-and-out fashion as they cross to form a tubular member defining asingle lumen. The pitch angle of the braid may be changed at the timethe braid is woven or at the time the braid is included in the cathetersection.

The coil and braid stiffeners shown in FIGS. 4-6 may be used alone or incombination to form a composite stiffener for the catheter of thepresent invention, as shown in FIGS. 2, 3, and 7, and described below.

The catheter portion of FIG. 2 includes first and second stiffenerswhich are both in the form of a helically wound coil. The secondstiffener comprises a non-metal ribbon 142 helically wound in onedirection on the inner liner 132 and the first stiffener comprises ametal ribbon 140 helically wound in an opposite direction on the secondstiffener. An outer cover 134 is placed over the stiffeners. The metalribbon 140 is only wound onto the proximal section of the catheter. Thisconstruction provides a reduction in stiffness in the distal sectionwhile providing a smooth transition between the two sections. Inconventional catheters the proximal and distal sections often comprisetwo different stiffeners having different materials and differentconfigurations. Since the only difference between the proximal section124 and the distal section 128 is the elimination of the metal stiffener140, there is no sharp transition which may affect catheter performance.The metal ribbon 140 in the proximal section provides kink-resistance,and increases the stiffness in the proximal section 124, thus improvingpushability. The non-metal ribbon 142 in the distal section 128 provideskink-resistance and permits reshaping of the section upon exposure tosteam, as previously discussed.

It is to be understood that the arrangement of the coils may be otherthan the one shown in FIG. 2. For example, as shown in FIG. 2A, themetal ribbon 140 may be first wound on the inner liner 132 and thenon-metal ribbon 142 wound on top of the metal ribbon in the proximalsection of the catheter. The non-metal ribbon 142 would then assist inholding down the metal ribbon 140. This lessens the tendency of themetal ribbon 140 to unwind and hence create bumps. The metal andnon-metal ribbons 140, 142 may also be wound in the same direction, withribbons being located adjacent one another. One or both of thestiffeners may also be formed with a double ribbon wind (not shown). Fora double ribbon wind, a pair of ribbons is placed side by side andtreated as a single ribbon. The braid is denser than the single ribbonwind. The number of ribbons, thickness of the ribbons, and pitch mayalso vary to further fine tune the stiffness of the catheter in theparticular sections. FIG. 8 illustrates an embodiment where the pitch ofribbon 140 is varied.

FIG. 3 schematically shows an alternative embodiment 122 of the catheterportion 120 of FIG. 2. The catheter portion 122 includes the inner liner132, outer cover 134, a first stiffener, and a second stiffenerinterwoven to form a braid member. The first stiffener comprises a metalribbon 160 and the second stiffener comprises a non-metal ribbon 162.The two ribbons 160, 162 are woven together in the proximal section 126and when the distal section 130 is reached, the metal ribbon isterminated and only the non-metal ribbon is wound in the distal section.Instead of eliminating the metal ribbon 160 from the braid during thebraiding process, the braid may be formed as a continuous member withboth the metal and non-metal ribbons along the entire length of thebraid member. The metal ribbon 160 may then be pulled from the braid inthe distal section 130 during assembly of the catheter.

The braid may be interwoven from a single metal ribbon and a singlenon-metallic ribbon or a plurality of metal and non-metal ribbons.Commercial braiders are typically configured for producing eight orsixteen ribbon braids. The braid may be formed, for example, on abraider with four spools having metal ribbons and four spools havingnon-metal ribbons to produce a four stranded metal and four strandednon-metal braid. There may also be an uneven number of metal andnon-metal ribbons (e.g., six metal ribbons and two non-metal ribbons).The metal and non-metal spools for the braider may be positioned suchthat the metal ribbons are all wound only in one direction with thenon-metal ribbons wound in the opposite direction, or the spools may bepositioned so that the metal and non-metal ribbons are intermixed withboth types of ribbons being wound in each direction. It should be notedthat if all non-metal ribbons are wound in only one direction, thedistal section will have a coil stiffener rather than a braidedstiffener. Alternatively, the first stiffener may comprise a braidformed from only metal ribbons and the second stiffener may comprise abraid formed from only non-metal ribbons. One braid is then positionedover the other braid in the proximal section, and only the non-metalbraid is located in the distal section.

FIG. 7 schematically shows an alternative embodiment of the catheterportion 120 of FIG. 2. The catheter portion includes a proximal section170 having a stiffener comprising a non-metal ribbon 174 helically woundon the inner liner 132. A metal ribbon 172 is helically wound on thenon-metal ribbon 174. A distal section 176 of the catheter portionincludes the non-metal ribbon 174 wound on the inner liner 132. Theouter cover 134 is placed over the stiffeners in both the proximal anddistal sections 170, 176. The non-metal ribbon 174 is wound in theproximal section 170 with the rectangular cross-section of the ribbonextending generally parallel to a longitudinal axis A of the catheter.The ribbon 174 is rotated in the distal section 176 so that therectangular cross-section extends generally perpendicular to thelongitudinal axis A. The ribbon 174 may also be wound in the proximalsection 170 in the same orientation as in the distal section 176, forexample. The non-metal ribbon 174 may also be positioned over the metalribbon 172 in the proximal section, as previously discussed.

The metal stiffener is preferably formed from a metal alloy, such asstainless steel, tantalum or its alloys, tungsten, platinum, gold,copper, palladium, rhodium, or a superelastic alloy. Preferredsuperelastic alloys include the class of nickel/titanium materials knownas nitinol, disclosed in U.S. Pat. Nos. 3,174,851; 3,351,463; and3,753,700. Commercial alloys containing up to about 5% of one or moreother members of the iron group, e.g., Fe, Cr, Co, are considered to beencompassed within the class of superelastic nickel/titanium alloyssuitable for use. When using a superelastic alloy, an additional heattreat step may be desirable to preserve the shape of the stiffener. Thestiffener is placed on a mandrel and then heated to a temperature of650°-900° F. for a few minutes. After heat treatment, the stiffenerretains its shape and the alloy retains its superelastic properties.

Desirable non-metal materials for the second stiffener include PEBAX,Peek, polyimide, liquid crystal polymers (LCP) such as VECTRAN,polyethylene, polyethylene terephthalate and Nylon. Other suitablenon-metallic materials include polymeric materials such as polyester,polypropylene, carbon fiber, polyaramids (e.g., KEVLAR), and lowerperformance polymers such as DACRON.

The ribbons are preferably between 0.3 mil. and 3.5 mil., and morepreferably between 0.75 mil. and 1.5 mil. in thickness, and 2.5 mil. and12.0 mil. in width. For superelastic alloys, particularly nitinol, thethickness and width may be somewhat finer, e.g., down to 0.5 mil. and1.0 mil., respectively. The width of the ribbons may vary to providespecific stiffness requirements at different locations along the lengthof the catheter. The stiffeners may also be formed from a wire having acircular cross-sectional area.

Preferred polymeric materials for the inner liner 132 includefluoropolymers including PTFE, FEP, vinylidene fluoride, polyethylene,polyvinyl chloride (PVC), ethyl vinyl acetate (EVA), polyethyleneterephthalate (PET), polyimide, polyamide, polypropylene,polyfluorocarbons, polyurethane (CARBOTHANE), polyether block amide(PEBAX), styrene-ethylene/butylene-styrene (SEBS),styrene-butadiene-styrene (SBS), polysulfone, and their mixtures,alloys, copolymers and block copolymers. Another useful class ofpolymers is thermoplastic elastomers, including those containingpolyesters as components. Typical of this class is HYTREL. The innerliner 132 may be coated onto the inner surface of the stiffener.Polyesters and polyimides, in particular, are useful as adhesives inthis service. The wall thickness of the inner liner 132 may be between0.3 mil. and 3.0 mil., for example.

The outer cover 134 may be made of polyethylene or of EVA or theirmixtures, for example. Preferred polymeric materials for the outer cover134 include polyimide, polyamide, polyethylene, polyurethane, polyvinylchloride, polypropylene, fluoropolymer including PTFE, FEP, vinylidenefluoride, and their mixtures, alloys, copolymers, and block copolymers.The polymer is typically extruded into a tubing of appropriate size andthickness and then crosslinked to raise the melt temperature of theresulting tubing. The tubing is then inflated and perhaps stretched togive the included polymer a specific molecular orientation. The tubing,so treated, may then be slipped over the combination of inner liner 132and stiffener and heat shrunk into place. Heat shrunk tubing may befurther heated to shrink the tubing in such a way that it fills theinterstices between the windings of the ribbon. This allows the outercover 134 to directly contact the inner tubular liner 132. Even moredesirably, the outer cover 134 should be further heated to allow mixingof the outer cover with the inner liner 132 at their interface so as toform a strong integral catheter section. If a section with even moreflexibility is required, the outer cover 134 may also be of a memberselected from a more flexible material such as polyurethane(CARBOTHANE), low density polyethylene (LDPE), polyvinyl chloride,polyurethane, polyether block amide (PEBAX),styrene-ethylene/butylene-styrene (SEBS), styrene-butadiene-styrene(SBS), and other polymers of suitable softness or modulus of elasticity.The wall thickness of the outer cover 134 may be between 0.5 mil. and 10mil., for example.

The outer cover 134 may also be applied by dipping the inner liner 132and stiffener ribbon into a molten polymer bath or into a polymerdissolved in a solid or into a suspension or latex comprising the outercover polymer. The outer cover 134 may also be placed on the catheter byspraying or otherwise applying the material.

The inner tubular liner 132 and outer cover 134 may each be formed astwo separate members for the proximal and distal sections (i.e.,proximal and distal inner tubular liners, and proximal and distal outercovers). The material of proximal inner tubular liner may be selected tohave a higher stiffness than the material of the distal inner liner. Theinner liner may also be omitted particularly in the more proximalsection, since the majority of materials which are suitable for the moreproximal section are very hard and suitably slippery for passage ofguidewires 112 and the like.

It is to be understood that the materials and thickness of the innerliner 132 and outer cover 134 may be different than described hereinwithout departing from the scope of the invention. Furthermore, each ofthe polymers noted herein may be used in conjunction with radiopaquefiller materials such as barium sulfate, bismuth trioxide, bismuthcarbonate, powdered tungsten, powdered tantalum, or the like so that thelocation of various portions of the catheter sections may beradiographically visualized within the human body.

The exterior surface of the outer cover 134 and the inner surface of theinner liner 132 may be coated with a lubricious layer which ischemically bonded or is physically coated on the surface. Polymers whichinherently adhere to each other may be used for the inner liner 132 andouter cover 134 (e.g., certain polyethylenes and polyimides, orthermoplastics, which are miscible with one another upon appropriateheating, such as Pebax and polyurethanes). The exterior and interiorsurfaces of the catheter or catheter section may be coated with alubricious layer such as a hydrophilic polymer layer, which is eitherchemically bonded to the layer or is physically coated on the surface.

The number and type of sections of the catheter may vary. The cathetersections may have multiple polymeric layers exterior of the stiffener aswell as multiple polymeric liner members interior to the stiffener. Thecatheter sections may also include multiple layers of stiffeners betweenor amongst the various polymer layers.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A medical device, comprising: an elongatecatheter shaft having a proximal region and a distal region; a firststiffener disposed along both the proximal region and the distal region;wherein the first stiffener includes a non-metallic ribbon extending atleast partially circumferentially about the catheter shaft; a secondstiffener disposed along the proximal region, the second stiffenerincluding a metallic ribbon, wherein the first stiffener is interwoventogether with the second stiffener; wherein the distal region of thecatheter shaft is free of the second stiffener; wherein the cathetershaft has a first flexibility along the proximal region; and wherein thecatheter shaft has a second flexibility along the distal region that isdifferent from the first flexibility.
 2. The medical device of claim 1,wherein the first stiffener extends helically about the catheter shaft.3. The medical device of claim 2, wherein the first stiffener has aconstant pitch along the catheter shaft.
 4. The medical device of claim2, wherein the first stiffener has a variable pitch along the cathetershaft.
 5. The medical device of claim 1, wherein the metallic ribbonextends at least partially circumferentially about the catheter shaft.6. The medical device of claim 5, wherein the second stiffener extendshelically about the catheter shaft.
 7. The medical device of claim 5,wherein the metallic ribbon has a constant pitch along the proximalregion of the catheter shaft.
 8. The medical device of claim 5, whereinthe metallic ribbon has a variable pitch along the proximal region ofthe catheter shaft.
 9. The medical device of claim 1, wherein the firststiffener includes polyether block amide, polyetheretherketone,polyimide, liquid crystal polymer, polyethylene, polyethyleneterephthalate, nylon, polyester, polypropylene, or polyaramid.
 10. Themedical device of claim 1, wherein the first stiffener includes carbonfiber.
 11. A medical device, comprising: a tubular member having aproximal region and a distal region; a first stiffener disposed alongboth the proximal region and the distal region; wherein the firststiffener includes a polymeric ribbon that extends at least partiallycircumferentially about the tubular member; a second stiffener disposedalong the proximal region; wherein the second stiffener includes ametallic ribbon extending at least partially circumferentially about thetubular member; wherein the polymeric ribbon and the metallic ribbon areinterwoven together to define a braid comprising both the polymericribbon and the metallic ribbon along the proximal region; and whereinthe distal region of the tubular member is free of the second stiffener.12. The medical device of claim 11, wherein at least a portion of thepolymeric ribbon extends helically about the catheter shaft.
 13. Themedical device of claim 12, wherein the polymeric ribbon has a constantpitch along the tubular member.
 14. The medical device of claim 12,wherein the polymeric ribbon has a variable pitch along the tubularmember.
 15. The medical device of claim 11, wherein at least a portionof the metallic ribbon extends helically about the catheter shaft. 16.The medical device of claim 15, wherein the metallic ribbon has aconstant pitch along the tubular member.
 17. The medical device of claim15, wherein the metallic ribbon has a variable pitch along the tubularmember.
 18. The medical device of claim 11, wherein the first stiffenerincludes polyether block amide, polyetheretherketone, polyimide, liquidcrystal polymer, polyethylene, polyethylene terephthalate, nylon,polyester, polypropylene, or polyaramid.